Sotheby's forthcoming Contemporary Art Evening Sale in New York will feature one of the most important paintings by Francis Bacon to ever appear at auction.

Francis Bacon's Figure Writing Reflected in Mirror

Figure Writing Reflected in Mirror features a depiction of both Bacon and his lover George Dyer in a single figure, and was painted at the height of the artist's powers in 1976.

Described as a "very, very serious painting" by Sotheby's worldwide head of contemporary art Tobias Meyer in The Guardian, the piece is the most important work by Bacon to appear on the market since the record-breaking sale of Triptych 1976 in 2008.

Triptych 1976 broke the world record for a post-war painting at auction, selling for $86.28m to the Russian billionaire Roman Abramovich. Although several of his paintings have appeared at auction in recent years, none have been as highly regarded as Figure Writing Reflected in Mirror.

The painting was first exhibited along with Triptych 1976 at Bacon's legendary Paris exhibition in 1977. It was purchased by the current owner directly from the exhibition, and has remained in the same private collection for more than 30 years.

The painting is expected to achieve $30 - $40m when it crosses the auction block on May 9, but with the highly anticipated auction attracting international attention it has the potential to go far higher.